Braze furnaces are well known in the prior art for brazing aluminum heat exchanger workparts. The most common method of brazing such workparts according to the prior art includes conveying the workparts through a tubular muffle in which is established an isolated internal braze zone containing a braze conducive atmosphere. This braze conducive atmosphere is substantially devoid of oxygen to increase the size of the braze fillets and generally provide improved braze results. A conveyer means extends through the tubular muffle for conveying workparts through the braze zone. A radiation inducer means, typically an electric resistance wire, is disposed about the exterior of the muffle for heating the muffle to emit radiant heat energy into the braze zone. The muffle and radiation inducer means are surrounded by an outer insulative shell to reduce thermal loss. In this manner, the muffle is heated entirely by the external electric resistance wire, and radiates this heat to the workparts conveyed internally through the muffle. Such muffles are made sufficiently long and/or the conveyor means sufficiently slow enough so that complete brazing is accomplished prior to the workparts exiting the muffle.
These prior art muffle furnaces are deficient in that the electrical resistance wire, by nature, is slow to heat the massive muffle furnace to brazing temperatures, e.g., 1100.degree. F. to 1200.degree. F. Because of this slow heating of the muffle, efficiency dictates that the furnace be maintained at operating temperatures 24 hours per day, with workparts being passed through on a nearly continuous basis for energy conservation. Thus, for very small production runs, test runs, etc., the prior art muffle furnaces are very uneconomical.
Also, because the prior art muffle furnaces are generally quite long to allow the full and complete brazing of workparts conveyed therethrough, a significant amount of floor space is occupied by the furnace assembly. Because of the very long muffle furnace, it is more difficult to control atmosphere leaks and oxygen infiltration into the isolated internal braze zone. Other disadvantages naturally resulting from the extended length of the prior art muffle furnace include the increased thermal expansion and contraction of the muffle. Also, the long muffles of the prior art muffle furnaces require a correspondingly long conveyer means extending the length thereof, which translates into larger drive motors and the like to drive the conveyor means.
These and other disadvantages of the prior art muffle furnaces indicate a need for a braze furnace assembly which is shorter in length and more quickly heated to a brazing temperature so that small production runs and test runs may be carried out with efficiency.